Does Emacs support stripping comments in CLI mode?

Question

While researching how to remove C and C++ style comments from a file, I stumbled on the following two comments by Alan Mackenzie from almost 20 years ago:

I can assure you, as half of the Emacs CC Mode team (which includes full support for AWK, by the way ;-), that C Comments can be recognised without parsing the language beyond the level of comments and strings. C comments can be fully recognised by regular expressions (because, containing no unbounded nesting, they are finite-state mechanical), though those regexps are considerably more involved than one might at first expect.

The proof of the pudding is in the eating - Load a file.c into Emacs, and its comments get correctly "fontified" (syntax highlighted), no matter how cleverly you attempt to confuse it. Emacs does not contain a C compiler.

But you'd probably be better off following the suggestion of using the C preprocessor to eliminate the comments. Or maybe you could use Emacs, searching for blocks of text fontified with font-lock-comment-face, and deleting these.

and I, being a beginner Emacs user, have the same question as Ed Morton:

Also, the main point here is to strip C comments, so let us know if emacs can do that with a flag and without going into a GUI editting mode. If so, and I knew where to get the tool, I'd probably use that one tool rather than the chain of sed/gcc commands I posted elsethread.

Currently, I'm borrowing a very complex sed script to do the job, but still it fails in some very edge cases. I dismissed the C preprocessor method because doing that in a reasonably side effect free way requires GCC with support for some options that are only available in select platforms. Also, I later found out that the files I want to remove comments from also support Python style comments, and there is no way I'm modifying that IQ-200 sed script, but it seems rather easy to do in Emacs.

My question is, is there a way to strip comments of the forms /*comment*/, //comment and #comment using only the command-line interface through a pipeline of Emacs scripts and Unix utilities?

Answer 1

[Not an answer. I just wanted to give a couple of examples that are ambiguous and need to be nailed down more precisely, before a "correct" program can be written; comments are not suitable for that.]

Consider a file containing this text:

Some text

// some comment # containing an octothorpe /* and what looks like a C-style
* comment that extends across multiple lines
*/

/* A C-style comment that extends
across multiple lines and
# contains an octothorpe on the last line of the comment */

Some more text

/* A C-style comment */

What should the output of the program be when given this input? Note that this has nothing to do with Emacs: you would have to specify the output before any program (Emacs, sed, bash , Rust, Go, whatever) can be written. And there might be more ambiguities that need to be specified. That's what I mean by "exact": whether you use a formal grammar, or a description in English I don't much care, as long as you cover all the cases.